Before the video memory manager can manage the address space of the GPU, the display miniport driver must describe the GPU's address space to the video memory manager by using memory segments. The display miniport driver creates memory segments to generalize and virtualize video memory resources. The driver can configure memory segments according to the memory types that the hardware supports (for example, frame buffer memory or system memory aperture).

Commit limit on aperture segment
The amount of system memory that the video memory manager allows display miniport drivers to pin down (that is, the amount of system memory that display miniport drivers can memory map through an aperture segment) for GPU use at any given instant. The total amount of system memory that is allocated for the GPU might exceed the commit limit greatly; however, the video memory manager ensures that only up to a commit limit amount is actually resident in an aperture segment at any one time.

A linear aperture-space segment is similar to a linear memory-space segment; however, the aperture-space segment is only an address space and cannot hold bits. To hold the bits, system memory pages must be allocated, and the address-space range must be redirected to refer to those pages.

The driver is not required to specify all video memory resources that are available to the GPU in its memory segments; however, the driver must specify all memory resources that the video memory manager manages among all processes running on the system.

Mapping a memory range smaller than the framebuffer memory, then bank switching as necessary.

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Also, do you guys think I should replace my video card? Or is replacing the memory going to be enough

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Dynamic address translation

If, while executing an instruction, a CPU fetches an instruction located at a particular virtual address, fetches data from a specific virtual address or stores data to a particular virtual address, the virtual address must be translated to the corresponding physical address. This is done by a hardware component, sometimes called a memory management unit, which looks up the real address (from the page table) corresponding to a virtual address and passes the real address to the parts of the CPU which execute instructions. If the page tables indicate that the virtual memory page is not currently in real memory, the hardware raises a page fault exception (special internal signal) which invokes the paging supervisor component of the operating system (see below).